The present invention relates to a film advance mechanism for perforated film in photographic cameras.
Devices of this type usually serve to transport the film through a certain distance, dependent on the image format, after each exposure. In order to always achieve the same spacing between exposures, it is known that a film transport sprocket, which acts together with a ratchet mechanism, engages in the film perforation. Besides the disadvantage that, in this type of device, the film undergoes a shear stress, an exact position of the film is also not guaranteed by the freely rotating film transport sprocket.
In German Offenlegungsschrift No. 3,222,985, a device has therefore already been proposed in which a centering pin, controlled by the film movement itself and by the flash synchronization contact on the camera, engages in the perforation of the film. Control of such a device is technically complicated. In addition, the shear stress of the film increases, which results in frequent tearing of the perforation holes with the result that the film can no longer be advanced.